Electronic devices normally operate using direct current (DC). Most homes and buildings supply alternating current (AC) through wall outlets. Transformers are used to convert the AC power from the wall outlet into DC power used by most electronic devices. Such transformers are often integrated into an electronic device. An electronic device that plugs directly into a wall outlet (i.e., with an integrated power supply) must normally pass a certification process in order to be sold in many markets, such as the United States. Certifying an entire product is both expensive and time consuming.
Many companies will implement an external transformer, sometimes called a “wall wart”, to avoid certifying a particular product. Such external power supplies have a cord that has the transformer either positioned at the plug or positioned somewhere in the middle of the cord. Such external transformers are not part of the device, but rather plug into the device. In such an arrangement, the external transformer would need to be certified, but the device would not need to be certified. However, with devices such a speaker systems, external transformers add to the clutter of cords found in many consumer installations. Cord clutter is aesthetically undesirable and often leads to compromises in an audio installation.
It would be desirable to implement a speaker system that has the advantages of being plugged directly into a wall outlet while maintaining the advantages associated with having a third party certified external transformer/power supply.